package TestGoogleMaps;

# JSON-RPC service package
# calculate a distance between 2 points.
#
# See also  : http://www2.neweb.ne.jp/wd/nobuaki/New_Homepage/okinawa703.htm
#
# copyright : makamaka[at]donzoko.net
# license   : same as Perl's one

use strict;
use constant PI => 3.14159265358979;

sub echo {
	my $server = shift;
	my ($arg)  = @_;
	return sprintf("%.3f (km)", distance( @$arg ));
}


sub distance {
	my ($d1, $d2) = @_;
	my ($latA, $lonA, $latB, $lonB) = ($d1->{y}, $d1->{x}, $d2->{y}, $d2->{x});

	my $pA = geographic2geocentric($latA);
	my $pB = geographic2geocentric($latB);

	my $cosDelta
	 = cos($pA) * cos($pB) * cos(($lonA - $lonB) * PI / 180) + sin($pA) * sin($pB);

	my $sinDelta = sqrt(1 - $cosDelta ** 2);
	my $rad      = atan2($sinDelta, $cosDelta);

	$rad * 6369; # (km)
}


sub geographic2geocentric {
	my ($lat) = @_;
	return ($lat * PI / 180) - ((11.55/60) * PI / 180) * sin(2 * $lat * PI / 180);
}


1;